RESEARCH ARTICLE The OJIP fast fluorescence rise characterizes Graptophyllum species and their stress responses Le Buu Thach Æ Alison Shapcott Æ Susanne Schmidt Æ Christa Critchley Received: 8 December 2006 / Accepted: 28 May 2007 / Published online: 7 August 2007 Ó Springer Science+Business Media B.V. 2007 Abstract Causes for rarity in plants are poorly under- stood. Graptophyllum reticulatum is an endangered en- demic species, and it has three close relatives with different conservation status: the vulnerable G. ilicifolium, the rare G. excelsum, and the common G. spinigerum. Applied to the chlorophyll a fluorescence transient of leaves, the JIP test provides a Performance Index (PI) which quantifies the main steps in photosystem II (PSII) photochemistry including light energy absorption, excitation energy trap- ping, and conversion of excitation energy into electron flow. The PI is calculated from three components which depend on the reaction center density, the trapping efficiency, and the electron transport efficiency. PI was measured in the natural habitats of the four species and under artificially imposed environmental stresses in the glasshouse to determine whether conservation status was related to stress resilience. The results showed that soil type is unlikely to restrict the endangered G. reticulatum, vulnerable G. ilicifolium, or rare G. excelsum because PI was similar in plants grown in diverse soils in the glass- house. Photoinhibition is likely to restrict the endangered G. reticulatum to shade habitats because PI was signifi- cantly reduced when plants were exposed to more than 15% ambient light in controlled experiments. Water availability may determine the location and distribution of the vulnerable G. ilicifolium and common G. spinigerum because PI was reduced more than 60% when plants were exposed to water stress. While the characteristics of their natural habitats correspond to and explain the physiological responses, there was no obvious relationship between conservation status and environmental resilience. PI can be used to monitor vigor and health of populations of plants in the natural habitat. In cultivation experiments PI responds to key environmental variables that affect the distribution of species with conservation significance. Keywords Fv/Fm ratio  JIP test  Graptophyllum  Performance Index  Photosynthesis  Rarity  Stress Abbreviations ABS absorbance C common Chl chlorophyll CS cross section DI dissipation E endangered ET electron transport Fm maximum fluorescence level Fo minimal fluorescence level Fv/Fm maximum quantum yield of PSII photochemistry PEA Plant Efficiency Analyser PI performance index on absorption basis PPFD photosynthetic photon flux density PQ plastoquinone PSII photosystem II Q A primary electron acceptor of PSII R rare RC reaction center RWC relative water content TR trapping V vulnerable Le B. Thach  S. Schmidt  C. Critchley (&) School of Integrative Biology, The University of Queensland, Brisbane, QLD 4072, Australia e-mail: c.critchley@uq.edu.au A. Shapcott Faculty of Science, Health & Education, University of the Sunshine Coast, Maroochydore D.C, QLD 4558, Australia 123 Photosynth Res (2007) 94:423–436 DOI 10.1007/s11120-007-9207-8